Reference is made to FIG. 1, which is a simplified illustration of a prior art steering wheel. A steering wheel 400, shown in FIG. 1, includes a circular gripping member 401, one or more connecting members 402-404 that connect the gripping member 401 to steering column 407, and buttons 405 and 406 on connecting members 402 and 403 for controlling various devices in the vehicle. Connecting members 402-404, which connect gripping member 401 to steering column 407, are also referred to as spokes. In FIG. 1, button 405 is used to answer an incoming phone call on the vehicle's BLUETOOTH® speaker phone and button 406 hangs up the call. BLUETOOTH is a trademark owned by the Bluetooth SIG of Kirkland, Wash., USA. Controls mounted in a steering wheel can be operated comfortably and safely since the driver is able to control and operate these controls without taking hands off the wheel or eyes off the road.
Historically, the first button added to a steering wheel was a switch to activate the car's electric horn. When cruise control systems were introduced, some automakers located the operating switches for this feature on the steering wheel as well. Today additional button controls for an audio system, a telephone and voice control system, a navigation system, a stereo system, and on board computer functions are commonly placed on the steering wheel.
U.S. Patent Publication No. 2012/0232751 A1 for PRESSURE SENSITIVE STEERING WHEEL CONTROLS describes adding pressure-sensitive controls to the circular gripping member of the steering wheel. Pressure sensors are located at various locations along the perimeter of the gripping member, and different locations correspond to different controls. A control is actuated in response to application of pressure at a sensor location, e.g., by the user tightening his grip.
Prior art user interfaces associated with steering wheels, such as the buttons and grips discussed hereinabove, associate a function with an absolute position on the steering wheel. This is conceptually analogous to a touch-sensitive screen displaying icons where the user touches the location on the screen at which the icon is located to activate the icon. The concept of absolute positioning for user input goes back even further: each key on a keyboard is positioned at an absolute position within the keyboard. Similarly, early graphical user interfaces using light pens required the user to place the light pen onto a graphic displayed on the screen in order to activate a corresponding function.
In contrast to these user interfaces based on absolute positioning, the computer mouse introduced a user interface for controlling a cursor based on relative positioning. Namely, the mouse cursor moves on the screen in a direction that the mouse moves from point A to point B, but this movement is not at all contingent on the actual coordinates—the absolute positions—of points A and B. This shift from absolute positioning to relative positioning frees the user from having to look at, or be aware of, the location of the mouse on the table. The user only has to control the direction in which the mouse moves on the table, which he can do without looking at the mouse. One of the objectives of the present invention is to provide a user interface for a driver based on the relative positioning user interface model.